Neural modulation has been proposed as a therapy for a number of conditions. Often, neural modulation and neural stimulation may be used interchangeably to describe excitatory stimulation that causes action potentials as well as inhibitory and other effects. Examples of neuromodulation include Spinal Cord Stimulation (SCS), Deep Brain Stimulation (DBS), Peripheral Nerve Stimulation (PNS), and Functional Electrical Stimulation (FES). SCS, by way of example and not limitation, has been used to treat chronic pain syndromes. Some neural targets may be complex structures with different types of nerve fibers. An example of such a complex structure is the neuronal elements in and around the spinal cord targeted by SCS.
SCS and dorsal root ganglia (DRG) stimulation have been proposed to alleviate pain. A therapeutic goal for conventional SCS programming has been to maximize stimulation (i.e., recruitment) of the dorsal column fibers.
Neuropathic pain patients may not experience adequate pain relief from drugs, or even from spinal cord stimulation (SCS) in many cases. Contributing to the problem is that pain signals communicate via slow-moving unmyelinated type C fibers. Neither SCS nor DRG stimulation achieve maximal coverage of these fibers. Unmyelinated fibers require higher amplitude stimulation to induce action potentials in comparison to myelinated fibers. However, delivery of high amplitude stimulation delivered as part of SCS from the epidural space or delivered proximate to the DRG may be intolerable when other neuronal elements are modulated in the region.